manager: Fix complete_command_cb() compile errors
Under Void Linux the following were seen with GCC 10.2:
../src/cad-manager.c: In function 'complete_command_cb':
../src/cad-manager.c:51:13: error: a label can only be part of a statement and a declaration is not a statement
51 | CallAudioMode new_audio_mode = GPOINTER_TO_UINT(op->value);
| ^~~~~~~~~~~~~
../src/cad-manager.c:65:13: error: a label can only be part of a statement and a declaration is not a statement
65 | CallAudioSpeakerState new_speaker_state = GPOINTER_TO_UINT(op->value);
| ^~~~~~~~~~~~~~~~~~~~~
../src/cad-manager.c:73:13: error: a label can only be part of a statement and a declaration is not a statement
73 | CallAudioMicState new_mic_state = GPOINTER_TO_UINT(op->value);
| ^~~~~~~~~~~~~~~~~